相变及空位缺陷对高压下BeO光学性质的影响

Influence of phase transformation and vacancy defects on optical properties of BeO under high pressure

为了探究BeO晶体能否成为冲击波实验中的候选窗口材料,本文采用密度泛函理论(DFT)的第一性原理方法,计算了150 GPa的压力范围内BeO理想晶体和含氧空位点缺陷晶体的光学性质.吸收谱数据显示,BeO高压结构相变对其吸收谱的吸收边几乎没有影响.并且,在150 GPa压力范围内,BeO理想晶体在可见光区没有光吸收行为.氧空位点缺陷的存在将使得其吸收边出现明显的红移现象,但在可见光区仍然没有光吸收(是透明的).波长在532 nm处的折射率数据表明:在BeO的WZ和RS结构相区,其折射率会随着压力增加而缓慢降低,而高压结构相变和氧空位缺陷将使得其折射率显著增大.计算数据分析表明BeO有成为冲击窗口材料的可能,并且本文所获信息将对未来进一步的实验有重要参考价值.

In order to explore whether BeO crystal could be a window material in shock wave experiments,the optical properties of BeO crystal without and with oxygen-vacancy defects within pressure 150 GPa were calculated using the first-principles method based on density functional theory(DFT).The absorptive data suggest that the high-pressure phase transition in BeO affects hardly its absorptive edge,and within pressure 150 GPa there is no light absorption in the visible region for its perfect crystal.The presence of the oxygen vacancy point defect in BeO causes an obvious red-shift in its absorption edge,but there is still no light absorption in the visible region(transparent)for defect crystals.The refractive-index data at 532 nm show that:in the WZ and RS phase regions of BeO,the refractive index decreases slowly with increasing pressure,but the high-pressure structural transition and vacancy defect in BeO will cause its refractive index an obvious increase.Our analysis indicates that BeO is likely to be a shock window material,and the calculated results would provide some important information for further experimental study.